I've also heard of the "drip and seep" method but never quite understood it. Anyhow, what I do is put a couple of drops--literally just 1 or 2--of light vegetable oil in my hand, rub to warm it, and apply to the whole jo. same w/ bokken. I'm probably doing something wrong though (wry smile)

The problem with vegetable oil (or any cooking oil) is that it spoils - goes rancid. Any kind of mineral oil should be OK - even baby oil, which is just mineral oil with a little fragrance.